The objectives of this project are to describe the development of mutant and inbred animals with genetically produced congenital malformations, particularly those of the oral region, and to examine the interaction between the tissues of these animals in the developmental processes in order to determine the nature of the mechanism producing the genetic defect. Several methods will be employed. A survey of mouse mutants is being undertaken to examine their oral structures in relation to those of the lines from which they arose. Mutants of specific interest are being collected, and colonies of these animals are to be developed as a basis for experimental study. Timed matings are being made to produce animals of known gestational age. Serial sacrifice and histological study are used to produce documentation of the developmental processes. Assays of hormonal levels during pregnancy and during teratogenic stimulation are being carried out to evaluate the effects of hormones on development of defects. Teratogenic drugs and dietary restrictions are being studied in specific genotypes of mutant and inbred animals to determine the mechanism of action of the defective genotype.